Factory automation (FA) devices known to control equipment or machines include programmable logic controllers (PLCs) or programmable controllers.
A PLC writes information, such as setting information, that is referred to by a control program for controlling equipment or machines into nonvolatile memory as appropriate, and reads the information when needed.
Japanese Unexamined Patent Application Publication No. 2010-176386 (Patent Literature 1) describes a technique for retaining a data area and a data value before data is written as well as a data area and a data value after the data is written in a redundant manner. Such redundant-data retaining technique intends to prevent corruption of information when power fed from an external power supply is cut, in the event of, for example, a power outage.